Understanding The Jicarilla Herd

Image captured by a JMHA field study trail camera.

                  ​Due to economic stress and other factors, finding quality adoptive homes for captured mustangs is increasingly difficult.
Therefore, controlling the wild population of mustangs is vital to their survival as an American icon. Fertility regulation is the most powerful tool we can use in this effort.  Having and maintaining accurate records of the wild horses is the primary step towards creating an effective fertility program.
​  JMHA is spearheading the study of the Jicarilla herd  in an effort to establish a fertility management plan that can be used as a template for other herds as well. 

The Challenges of PZP 

           Herd management through the use of fertility control has been around for some time.  The use of PZP(porcine zona pellucida) has been the most extensively studied method,(more information) and has proven to be an effective means of controlling mustang populations without the use of wild horse gathering. Yet, because of some of the challenges presented by PZP, the Forest Service and Bureau of Land Management have been slow to fully implement the use of PZP in regulating the herds under their care.  Below are some of the challenges that have hindered the governmental agencies' use of this humane option.

Timing

          While it poses no threat to an unborn foal, PZP is most effective in mares that are not in foal, or have never been pregnant.
Although a mare who has been dosed with PZP when she is in foal is less likely to conceive again, between pregnancies is the optimum time to administer PZP.  A mare can become pregnant again just one week after giving birth leaving a very narrow time frame to find her on the range and inject her for peak efficacy.
​ For this reason, knowing the correct time to inject a mare is important.   Keeping records of each mare and her pregnancies is the best way of maximizing the performance of PZP in the wild horses.

Boosters

Because PZP is an immunocontraceptive, or vaccine(more information), that causes a mare's immune system to create antibodies that make her infertile for a time. For best efficacy, a booster shot must be given between 3 and 6 weeks after the initial injection.  After approximately 10 months her antibody titers will begin to fall, and the mares must be re-injected. This pattern can be repeated safely for up to 4 years without serious risk of permanent infertility.
Again, accurate mare identification and record keeping are important factors in administering PZP.

Administering PZP

       Ideally, PZP is injected into the hip muscle, to do this a wild horse must either be trapped and restrained in stocks or darted.  Trapping  has the advantage that it is easier to keep track of giving the second booster, but it is costly, stressful, and has the potential for the horse to injure herself.  It does not take horses long to learn to avoid being trapped again.
Darting is the easier of the two choices, but keeping record of which mares have received injections becomes a much bigger task. The range of the darting device is about 30 yards and mustangs can quickly learn how to stay out of range.

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          At the heart of each of these challenges is the difficulties of accurate record keeping and insufficient manpower dedicated to the process of fertility management.  One solution to this lack of manpower has been for volunteer groups to take on the task of identifying and monitoring the horses in the mustang herds.
        This is where JMHA is stepping up to the challenge of help gather information on the Jicarilla herds.  JMHA's study of the herds, including the identification of individual horses, will be the keystone in forming strategies to control herd growth rates, and in stopping or reducing the gathers.

JMHA's Goals 

               After working for several years placing horses in good adoptive homes, we have come to be of the opinion that keeping the mustangs in the wild is in the best interests of the wild horses. The herd study program will help us achieve this goal.

Image captured by a JMHA field study camera.

Current progress on the herd study.

Image captured by a JMHA field study camera.

 
     Currently, with the approval of the Forest Service, we are using trail cameras to capture band pictures and GPS locations to develop a database for identifying individual horses. The information gleaned from the cameras will be instrumental in understanding the daily behavior of the bands. We need to learn where the horses get water, their travel paths, and areas where the bands graze or congregate.  Once we become familiar with the behavior patterns of the herd, blinds can be placed in locations that will allow the most mares to be darted in the least amount of time.
 Our data will be compiled and results of the study communicated to the Forest Service and others.   JMHA strongly believes that this data will demonstrate advantage of using hunting blinds in darting over other PZP administration methods, for ease of use and success rates. This will also validate the use of third parties for PZP application and management; as this work does not fit the work hours for the Government employees.

         At this time, we are in the process of  validating the use of hunting blinds in darting mustangs. As noted before, darting horses can be difficult as they learn to stay out range of the darting device.  It is our hope that the use of blinds will reduce this problem. Also, we want to show the blinds can alleviate some of the demands on on the darter's energy and resources, making it so the darters will be in the field a minimum amount of time, hiking over less terrain. 
          In 2021, the plan is to establish several locations to install hunting blinds and schedule trained darters to be in those blinds during prime herd movement times.   Darters will record all required documentation for the PZP program.  We want the darting will be done over the course of the fewest days possible in late winter and early spring. This way, the horses can be left alone for the rest of the year; experiencing the minimum amount of human interference possible.

Image captured by a JMHA field study camera.

Keep our mustangs wild!

You can help JMHA

 preserve our wild horses.

Our efforts to study the herd requires the use of a considerable amount of equipment and resources. 
 Also, until roundups and trapping can be abandoned in our area, we will  continue to assist in finding excellent homes for the horses gathered.  JMHA covers many of the expenses involved in training and caring for the mustangs we are trying to home. Your monetary gifts go entirely to helping horses!

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